title: Using a reference point and videokeratography for intraoperative identification of astigmatism axis.
abstract: OBJECTIVE
  To estimate the misalignment of the astigmatism axis caused by intraoperative identification of the axis without using reference points.
  
  
  METHODS
  Osaka University Medical School, Suita, Japan.
  
  
  METHODS
  This study included 38 eyes of 19 patients with no ocular pathology except refractive error and 32 eyes of 16 patients with cataract. A point was marked on the nasal conjunctiva, on the "intraoperative" horizontal axis as estimated by the examiner using a surgical microscope while the patient lay on the operating table in the supine position. Videokeratography was performed with the patient seated, and the degree of axial misalignment was determined by measuring the angle between the conjunctival mark and the horizontal axis identified on the video image.
  
  
  RESULTS
  Mean axial misalignment for all patients was 4.4 degrees +/- 2.8 (SD), which could theoretically cause about a 15% loss of surgical effect. The maximal misalignment was 14 degrees, which would correspond to a 48% loss of astigmatic correction.
  
  
  CONCLUSIONS
  The results of this study suggest that intraoperative identification of the astigmatism axis without using reference points may reduce the surgical effect because of axis misalignment. The use of a reference point and preoperative videokeratography may increase the accuracy of identification of the astigmatism axis.
authors.affiliation: Department of Ophthalmology, Osaka University Medical School, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Suzuki
authors.forename: N
authors.initials: N
authors.lastname: Maeda
authors.forename: H
authors.initials: H
authors.lastname: Watanabe
authors.forename: A
authors.initials: A
authors.lastname: Kiritoshi
authors.forename: Y
authors.initials: Y
authors.lastname: Shimomura
authors.forename: Y
authors.initials: Y
authors.lastname: Tano
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001251:Astigmatism / Q000175:diagnosis*; D003315:Cornea / Q000473:pathology*; D019781:Corneal Topography / Q000379:methods*; D006801:Humans; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D012015:Reference Standards; D015203:Reproducibility of Results